Note: Descriptions are shown in the official language in which they were submitted.
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GRINDING AI~RANGEME:NT
Field of the Invention
[0001] The invention concerns a grinding arrangement for a chopper
arrangement,
with a grinding stone for the grinding of the knives of the chopper
arrangement and a
moving arrangement for the movement of the grinding stone over the length of
the
knives, where individual locations of the knives can be associated with
differing
grinding times.
l3ackeiround ____of the Invention
[0002] U.S. Patent No. x.,$43,767 describes a grinding arrangement for a
chopper
arrangement, in which the grinding stone traverses the width of the chopper
drum
back and forth with constant velocity- At each of the reversal points at the
left and
the right end of the chopper drum, the grinding stone remains stopped for a
dwell
time so that at that location the knives of the chopper drum are ground over
an
interval of time that is longer than the grinding time that is associated with
the parts
of the knives located between the reversal points.
[0003] During the operation of a forage harvester, the knives fastened to the
chopper drum wear over time. While the knives around the circumference of the
chopper drum, as a rule, wear approximately at a unii°orm rate, the
wear across the
width of the chopper drum may vary evnsiderabfy. Mence the diameter of the
enveloping circle described by the cutting edges of the knives can vary in the
axial
direction of the shaft ofthe chopper drum. A cylindrical or slightly concave
shape is
desired in order to simplify an automatic adjustment of the shear bar or to
make this
possible in the first place, depending on the adjustment system. A parallel
and exact
in-feed of the shear bar towards the circumference ot~ the chopper drum is
indispensable for an effective chopping process.
[0004] With known grinding arrangements nv possibilities are provided to
equalize
automatically the deviations from the cylindrical shape of the chopper drum
during
the grinding process.
Summary of the Inventio_0
[0008 According to the present invention, there is ?provided an improved
grinding
arrangement far the knives of the chopper drum of a forage harvester.
[0006] An object of the invention is to provide an arrangement for controlling
the
movement of the grinding stone of a grinding arrang~:ment in such a way that
the
grinding time for each point along the length of the knife can be different.
.~..T,
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[0007] A more specific object of the invention is to provide an arrangement
for
controlling the movement of a grinding stone by selecting the path and time
characteristic of the movement of the grinding stone as desired so that the
grinding
stone operates longer on the locations of the knife at which it is worn
relatively little,
than on the locations at which it is worn relatively heavily.
[0008] Yet a more specific object of the invention is to provide an
arrangement for
controlling the movement of a grinding stone by establishing, and storing in
memory
in advance, grinding times based on empirical values (as result of tests) or
values
determined by experience, and by storing a desired target shape of the cutting
edges
of the knives.
[0009] These and other objects of the invention will become apparent from a
reading of the ensuing description together with the appended drawings.
Brief Description of the Drawings
[0010] FIGS. 1a - 1d are schematic views of chopper drums with knives worn to
produce different drum profiles.
[0011] FIG. 2 is a schematic left side view of a harvesting machine with a
chopper
drum with which a grinding arrangement constructed in accordance with the
present
invention is particularly adapted for use.
[0012] FIG. 3 is a front view of a first embodiment of a grinding arrangement.
[0013] FIG. 4 is a flow diagram that illustrates a grinding process.
[0014] FIG. 5 is a flow diagram that illustrates another grinding process.
Description of the Preferred Embodiment
[0015] FIGS. 1a - 1d will be described below in conjunction with the
description of
the operation of the grinding arrangement.
[0016] The harvesting machine 10 shown in FIG. 2 in the form of a self-
propelled
forage harvester is supported on a frame 12, that is carried by front and rear
wheels
14 and 16. The harvesting machine 10 is operated from an operator's cab 18
from
which a crop recovery arrangement 20 can be viewed and controlled. Crop taken
up
from the ground by the crop recovery arrangement 20, for example, corn, grass
or
the like, is conducted to a chopper drum 22 that chops it into small pieces
and
delivers it to a conveyor arrangement 24. The crop leaves the harvesting
machine
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to an accompanying trailer over a discharge duct 26, that is mounted for
rotating
about an upright axis. Between the chopper drum 22 and the conveyor
arrangement
24 a post-chopper reduction arrangement 28 is provided for use during the
harvesting of corn, the arrangement 28 operating to conduct the crop
tangentially to
the conveyor arrangement 24.
[0017] FIG. 3 shows a schematic view of a chopper drum 22 and a grinding
arrangement associated with it, as can be seen by a look at the harvesting
machine
10 in FIG. 2 from the front, with regard to the direction of forward travel.
The
chopper drum 22 is provided with a number of knives 38 distributed over its
width
and its circumference that chop crop taken up by the crop recovery arrangement
20
in interaction with a rigid shear bar 46. The chopper drum 22 includes a
central shaft
32 that can be driven in rotation through a belt pulley 36 at its end face and
belts, not
shown, by a motor of the harvesting machine 10. The shaft 32 is supported
through
two bearings arranged on each side of the chopper drum 22, not shown in FIG.
3, on
the frame 12 of the harvesting machine 10.
[0018] In order to be able to sharpen the knives 38 after a certain operating
time,
without having to disassemble the individual knives 38 or the entire chopper
drum
22, a grinding arrangement is provided above the chopper drum 22 close to the
enveloping circle described by the knives 38, which generally contains a
grinding
stone 42, a grinding stone retainer 40 associated with it and an axle 44, on
which the
grinding stone retainer 40 is supported in bearings so that it can be slid.
[0019] If the knives 38 are to be sharpened, the chopper drum 22 is brought
into
rotation, as a rule in the reverse direction of rotation and/or with reduced
rotational
speed, compared to normal chopper operation. The grinding stone retainer 40
with
the grinding stone 42 attached thereto is slid by means of a movement
arrangement
48 out of a rest or park position, not shown, in which it is arranged to the
side
alongside the chopper drum 22, over the entire width of the chopper drum 22.
At
that time, the underside of the grinding stone 42 is in contact with the
knives 38, and
sharpens these. During the grinding process, the grinding stone 42 traverses
the
width of the chopper drum 22 several times. The end points of this sliding
movement
are shown in FIG. 3 by the grinding stone retainer with the number call-outs
40 at the
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left reversal point and 40' at the right reversal point.
[0020] Between the sliding movements, an in-feed of the grinding stone 42 can
be
performed, that is, a minute movement of the grinding stone 42 towards the
knives
38. In the embodiment shown, a mechanical element, for example a ratchet gear,
is
used for this purpose which interacts with a stationary element upon reaching
one or
both reversal points of the grinding stone retainer 40. The rotation of the
mechanical
element is converted by means of a threaded component into a sliding movement
so
that the grinding stone 42 is fed-in towards the chopper drum 22. By a
movement of
the grinding stone 42 only through a limited sliding region towards the side,
an in-
feeding can be avoided, since the mechanical element then does not come into
contact with the stationary element. A grinding process of this type without
in-
feeding is appropriate for the planing at the conclusion of the grinding
process. The
movement arrangement 48 of the grinding arrangement is controlled by a control
arrangement 52, shown schematically in FIG. 3, which controls the sliding of
the
grinding stone 42 by means of the movement arrangement 48 as well as the in-
feeding, in the manner described above. The control arrangement 52 is supplied
with information about the immediate position of the grinding stone 42 which
can be
performed by a corresponding sensor, not shown in the drawing, for example, a
linear potentiometer which is integrated into the motor of the movement
arrangement
48, or by the control arrangement 52 having available information into which
position
it has brought the movement arrangement 48. For this purpose, for example, the
number of impulses that have been transmitted to a stepper motor of the
movement
arrangement 48 can be stored in memory. Furthermore, the control arrangement
52
can also control the drive of the chopper drum 22.
[0021] It should be noted that the in-feeding can be performed by a separate
motor,
in particular an electric or hydraulic motor that would also have to be
connected with
the control arrangement 52. In place of an in-feeding by shifting the grinding
stone
42, the entire grinding stone retainer 40 could be fed-in instead.
[0022] The control arrangement 52 is connected with a memory 54 and a knock
sensor 50 attached to the grinding stone retainer 40, used as a measurement
arrangement. A grinding process, as illustrated in FIG. 4, takes its course as
follows:
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[0023] After the beginning of the grinding process step 100, the control
arrangement 52 initially causes the grinding stone 42 in step 102 to be moved
by the
movement arrangement 48 to traverse the width of the chopper drum 22 and
return
again into the initial position. Here the grinding stone 42 can remain in the
position
relative to the grinding stone retainer 40 in which it was brought during the
preceding
grinding process, or, if necessary, in contrast thereto, fed-in towards the
chopper
drum 22. Step 102 can be used to determine whether an in-feeding of the
grinding
stone 42 is necessary. That is the case if no signal, or only a very minute
signal, is
generated by the knock sensor 50 in at least one location of the chopper drum
22. In
this case, there is a dent, depression or the like in the knives 38 that
cannot be
equalized without in-feeding.
[0024] During the traversing of the width of the chopper drum 22, the knock
sensor
50 attached to the grinding stone retainer 40 generates a signal that is a
function of
the spacing of the cutting edges of the knives 38 from the grinding stone 42.
The
control arrangement 52 is supplied over an appropriate analog/digital
converter with
information about the amplitude of this signal.
[0025] With a chopper drum 22 that has the shape shown in FIG. 1a, a signal
characterized in the following as a spacing signal, which contains information
about
the spacing, would decrease from left to right, with the amplitude of the
signal
transmitted by the knock sensor 50 increasing from left to right. In the case
of the
chopper drum 22 shown in FIG. 1 b, that can be the result of the crop supplied
or
excessive dwell time at the ends of the shifting movement of the grinding
stone 42
across the width of the chopper drum 22, so that the knives 38 are more
heavily
worn there, the spacing signal would continually decrease the closer the
grinding
stone 42 approaches the center of the chopper drum 22. If the shape is the
result of
long dwell times at the ends of the chopper drum 22, so that it can be
recognized by
the control arrangement 52 during the grinding, the dwell times stored in the
memory
54 can be shortened automatically. The shape of the chopper drum 22 shown in
FIG. 1c results in the largest spacing in the center, and the shape shown in
FIG. 1d
results in a spacing varying irregularly over the width, The shape in FIG. 1 c
can be
he result of dwell times at the end of the chopper drum 22 that are too short.
If this
CA 02353352 2004-07-22
is recognized by the control arrangement 52 during the grinding, the dwell
times
stored in the memory 54 can be extended automatically. However, the shapes
illustrated in FIGS. 1c and 1d can also be the result of non-uniform supply of
crop or
a defective shear bar 46.
[0026] In the grinding process shown in FIG. 4, the grinding stone 42 is
initially not
fed-in further. In step 104 the grinding stone 42 is brought into a first
position at the
chopper drum 22 by the movement arrangement 48, which, as a rule is adjacent
to
the park position and is located at the left or right outside. It remains in
this position
until the knock sensor 50 generates an output signal that corresponds to a
desired
spacing between the shaft 32 and the cutting edges of the knives 38 so that an
adequate sharpness of the cutting edges of the knives 38 interacting with the
grinding stone 42 is attained. Therefore, step 106 poses the question whether
the
signal of the knock sensor 50 is smaller than a threshold value. If the result
is "No",
step 106 follows, otherwise step 108. There the grinding stone 42 is
transported by
the movement arrangement 48 through a distance corresponding to its width
further
to the left or the right and grinds the knives 38 there. Step 110 follows in
which the
question is posed, whether the chopper drum 22 has already been processed over
its entire width. If "No", step 106 follows, otherwise the process is ended in
step 112.
Therefore the grinding stone 42 always remains standing at one location of the
chopper drum 22, until the knock sensor 50, in each case, transmits the
desired
output signal. These processes are repeated until the entire width of the
chopper
drum 22 has been processed. In this way, the result is that with varying
grinding
times across the width of the chopper drum 22, the chopper drum 22 is brought
into
a cylindrical shape. Upon a traversing of the width of the chopper drum 22
with the
grinding stone 42, the output signal of the knock sensor 50 would now be
constant.
In case the chopper drum 22 is found to have a particularly small radius at a
few
locations, so that the knock sensor 50 cannot detect any contact between the
knives
38 and the grinding stone 42, an in-feeding of the grinding stone 42 and a
repetition
of the grinding process over the entire width of the chopper drum 22 can be
performed. As a rule, the process described is repeated with reversed
direction of
movement of the grinding stone 42 and/or performed several times. To conclude
the
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grinding process, a normal grinding and/or planing for the entire chopper drum
22
can be performed in a manner known in itself. Finally, the grinding stone 42
is
brought into its park position.
[0027] FIG. 5 shows a time-sequence diagram for the control of the grinding
process 42 in which the grinding times varying over the width of the knives 38
are
stored in memory ahead of time. Thereby the sensor 50 shown in FIG. 3 can be
omitted. In the grinding process according to FIG. 5, after the start in step
120, the
grinding stone 42 is brought out of the park position at the left edge of the
chopper
drum 22 by the movement arrangement 48. Step 124 follows, according to which
the grinding stone 42 remains standing for a period t(x) that is a function of
its
immediate position x. The time intervals t(x) are stored in memory 54 in the
form of
a table, list, mathematical function or the like. Step 126 follows in which
the question
is posed whether the entire width of the chopper drum 22 has already been
traversed by the grinding stone 42. If this is not the case, step 128 follows
in which
the grinding stone 42 is traversed to the right through a distance 0x. The
distance
Ox corresponds preferably as a maximum to the width of the grinding stone 42,
so
that after a traverse of the chopper drum 22 all points of the knives 38 have
been
sharpened, however, it may be smaller than the width of the grinding stone 42.
After
step 128, step 124 again follows.
[0028] In case step 126 has determined that the entire width of the chopper
drum
22 has already been traversed, step 130 follows, in which a planing is
performed in a
manner known in itself. Following this, the grinding stone 42 is brought into
its part
position in step 132 and the grinding process ends in step 134.
[0029] It should be noted that the grinding stone 42 can also be returned to
the left,
with steps 124 through 128 corresponding to steps, however, in which the
grinding
stone 42 is moved to the left. The chopper drum 22 can also be traversed
multiple
times in the manner described. Instead of remaining stationary each time for a
certain length of time, the grinding stone 42 can be driven over the width of
the
chopper drum 22 with a velocity varying over the width of the chopper drum 22,
or
moved with a varying step pattern.
[0030] Having described the preferred embodiment, it will become apparent that
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various modifications can be made without departing from the scope of the
invention
as defined in the accompanying claims.
